Compasses.



C. F. MOONEY. COMPASSES. APPLSCATlON FILED lAN.19. 19x1.

Patent-ed Aug. 7, 1917..

2'0 or point, 14, detachably mounted. upon the v out nineteen As it is difficult to continue the scales on the outer leg-sections to the extreme outer.

ends thereof, I the main leg-sections, of the total length of place upon one or both of 1 and 2, an indication each leg from the axis of the pivotal connection, 3, to its extreme outer-end or point when the leg is fully contracted. Thus on each main leg-section I have placed the mark 6 in. indicating such length to be six inches.

The shank, 17, 'of each outer leg-section, 14, which telescopes within the respective main leg-section, 1 or 2, is also provided with a scale adapted to be read in connection with the outer end of said main leg-section to show the total length of the leg from the axis of the pivotal connection, 3, tothe extreme end or point of the leg when more or less extended.

Each outer leg-section terminates in a tip leg-section by means of a screw-chuck, 18, whereby points of. different kinds may be used in place of the particular form of points shown in the drawing.

The scale of circular measurement may appear upon one or both sides of the scaleplate, 4, or one side of the scaleplate may have the scale of circular measurement and the opposite side a scale of any other meas urement which may be desired.

The instrument above described is adapted for many uses by the machinist in plotting or laying off work where angular or circular measurements are involved.

For example: Let it be required to lay holes on a circle 14% inches in diameter. To do this, each leg is extended until the scale-reading on the shanks, 17, of the respective outer leg-sections indicates 7;} inches which would be the radius of said circle; and the outer leg-sections are locked in this position by meansof the set-screws, 15. The legs of the compasses are then spread apart until the reading on the scaleplate, 4, indicates 18gdegrees in which po sition the leg, 2, is locked to the scale-plate by means of the thumb-screw, 6.

The adjusting-nut, 8, is then turned until the reading of its circumferential scale indicates approximately 27 minutes, thus causing a slight further separation of the legs of the compasses, and causing their points to be separated approximately the distance between two holes spaced as required. The compasses may then be used as dividers to lay off upon the circle the nineteen holes required.

For angular measurements in degrees and half-degrees the scale-plate, 4, alone will ordinarily be found sufficient. When the measurement involves a smaller fraction of a degree, the adjusting-nut, 8, may be used.

merely necessary to adjust the length of the legs of the compasses to correspond with the radius of the circle, and then to what. ever angular degree the legs be opened, the distance between the points of the legs will in each case represent a corresponding angular distance between points on the circumference of said circle.

The scales on the main leg-sections make it Possible to determine angular or circular measurements with relationto circles having a radius less than the length of the legs of the compasses when contracted, as follows:

Let it be required to lay out sixteen points or holes on a circle, the diameter of which is 8 inches. The legs, 1. and 2, are separated until the reading on the scaleplate, 4:, indicates 22% degrees. The points of a pair of ordinary dividers are then stretched across the angle between the legs, 1 and 2, until one point ofthe dividers is located at the point of intersection of the 4- inch scale-line on the leg-section, 1, with the inner edge of said leg-section, and the other point of the dividers is located at the point of intersection of the 4-inch scale-line on the leg, 2, with the inner edge of that leg.

The dividers so spaced can be then used to lay off the properly located points on the circumference of the circle.

In employing divider points on the legs, as the points, 14*, said points are preferably inbent as shown .in the drawing, so that their apices are in the respective planes of the inner side surfaces of the legs, as shown, thus insuring accuracy in the use of the instrument as dividers.

What I claim as new and desire to secure by Letters Patent is 1. An instrument of the class described comprising a pair of flexibly connected legs each bearing a linear scale extending longitudinally thereof; and a scale-plate extending transversely of said legs in slidable relation to one thereof, said scale-plate being marked in units of circular measurement.

2. An instrument of the class described comprising a pair of flexibly connected extensible legs each bearing a linear scale whereby its length is indicated; and a scaleplate extending transversely of said legs in slidable relation to one thereof, said scaleplate being marked in units of circular measurement.

3. An instrument of the class described comprising a pair of flexibly connected legs each bearing a linear scale extending longitudinally thereof; and a scale-plate extending transversely of said legs in slidable relation to one thereof, said scale-' plate having a screw-- threaded shank extending through the other of said legs and being said last-mentioned 13a 1,235,715 v y i 3 scale indicating fractional partsof one of v 5 said units on said scale-plate.

4. An instrument of. the class described comprising a pair of flexible connected extensible legs, each comprising a plurality of leg sections, one longitudinally adjustable 1 upon the other, one of said leg-sections being provided with an index and the other with a linear scale, indicating with reference to g said index the total length of the leg" and a scale-plate extending transversely 05 said legs in slidable relation to one thereof, said ,15 scale-plate being marked inunits of circular measurement.

In testimony whereof, I have hereunto set my hand this 13th day of January, 1917.

CHARLES F. MOONEY. 

